The present invention relates to a working vehicle which allows variable transmissibility of traveling power which drives driving wheels.
Conventionally, in a working vehicle such as a construction machine, a power transmission system is known which interposes, between an engine and a torque converter, a modulating clutch flexibly changing a degree of engagement, and makes traveling power transmitted to the torque converter variable. FIG. 4 is a block diagram of a power transmission system disclosed in Japanese Patent Laid-open No. 11-230334, and a prior art will be described hereinafter, based on FIG. 4.
In FIG. 4, power of an engine 1 is distributed to a modulating clutch 2, hydraulic pumps 15 and 16 which drive the modulating clutch 2 and a working machine, respectively. Incidentally, the modulating clutch 2 is a xe2x80x9cclutchxe2x80x9d in the prior art. Power outputted from the modulating clutch 2 is successively transmitted to a torque converter 3, a transmission 4 and a drive shaft 5 to drive right and left driving wheels 7 and 7 through a differential 6.
The power transmission system is provided with a controller 8 for controlling a degree of engagement of the modulating clutch 2 and changes traveling power transmitted from the engine 1 to the torque converter 3. The drive shaft 5 is provided with a torque detector 9, and the controller 8 detects torque which drives the driving wheels 7 and 7, based on an output signal from the torque detector 9. An operator inputs set torque to the controller 8 from a torque setting dial 13, and the controller 8 controls the degree of engagement of the modulating clutch 2 so that the torque is to be this set value.
A vehicle body 10 of a working vehicle is provided with a vehicle speed detector 11, and the controller 8 detects vehicle speed based on an output signal from the vehicle speed detector 11. An operator inputs set vehicle speed to the controller 8 from a vehicle speed setting dial 14, and the controller 8 controls the degree of engagement of the modulating clutch 2 so that the vehicle speed is to be this set value.
An operator judges how much traveling power is the best according to the working situation and the road condition, based on his or her past working experience and knowledge. Additionally, he or she changes the degree of engagement of the modulating clutch 2 using the aforementioned torque setting dial 13 and the vehicle speed setting dial 14 to prevent a slip of the working vehicle and to improve operation efficiency by retarding vehicle speed of the working vehicle.
However, the above prior art has disadvantages as described below.
In the prior art, an operator judges whether the vehicle is in the slippery condition or not, and manually sets a degree of engagement of the modulating clutch 2 to control traveling power of the working vehicle. Accordingly, when an operator makes an error in this setting due to the immature ability or when an unexpected accident occurs, there is a case in which a slip of a vehicle cannot be surely inhibited simply with the prior art.
For example, setting torque or vehicle speed too high makes traveling power strong, thereby causing the disadvantage that torque driving the driving wheels 7 and 7 becomes too high and a working vehicle slips. Moreover, in working sites, when a working vehicle steps into the place where the soil quality is partially soft as a result of rain, wheels scraping out the ground, or the like, the grip of the driving wheels 7 and 7 suddenly changes, thereby causing the disadvantage that a slip cannot be inhibited simply under the aforesaid control.
The present invention is made in view of the aforesaid disadvantages, and its object is to provide a working vehicle with a power transmission system which surely prevents a slip of the working vehicle.
A working vehicle according to the present invention is a working vehicle having a modulating clutch which flexibly changes traveling power transmitted from an engine to a torque converter, and a controller which controls a degree of engagement of the modulating clutch, and it includes,
rotational frequency detectors which detect rotational frequencies of right and left driving wheels of the vehicle, respectively, and
the controller controlling the degree of engagement of the modulating clutch by detecting a sign of a wheel slip based on a difference in the rotational frequency between the right and left driving wheels detected by the rotational frequency detectors, to prevent a slip.
According to the aforementioned structure, a sign of a slip is detected based on the difference in the rotational frequency of the right and left driving wheels, and accordingly the degree of engagement of the modulating clutch is controlled to inhibit a slip. Therefore, a slip is not likely to occur since the controller detects a sign of a slip and automatically weakens the degree of engagement of the modulating clutch. Additionally, even if an operator makes a mistake in operating the modulating clutch, or the working vehicle steps into the place where the soil quality is unexpectedly soft and thereby a slip occurs, the slip can be certainly inhibited since the controller immediately weakens the degree of engagement of the modulating clutch. Accordingly, operation is carried out favorably to improve working efficiency, and at the same time the life of the wheels is lengthened.
Moreover, a working vehicle may be a working vehicle having a modulating clutch which flexibly changes traveling power transmitted from an engine to a torque converter, and a controller which controls a degree of engagement of the modulating clutch so that torque driving right and left driving wheels of the vehicle becomes a predetermined value during operation and it includes,
rotational frequency detectors which detect the rotational frequencies of the right and left driving wheels, respectively, and
the controller controlling the degree of engagement of the modulating clutch by detecting a sign of a wheel slip based on a difference in the rotational frequency between the right and left driving wheels detected by the rotational frequency detectors, to prevent a slip.
According to the above structure, torque is controlled to be a predetermined value, and a sign of a wheel slip is detected based on the difference in the rotational frequency between the right and left driving wheels, thereby the degree of engagement of the modulating clutch being controlled to inhibit a slip. As a result, torque is controlled in advance so that a slip is not likely to occur, and in addition, even if an operator makes a mistake in setting torque, or the working vehicle steps into the place of soft soil and thereby a slip occurs, the controller detects a sign of a slip and automatically controls the degree of engagement of the modulating clutch. Therefore, since a slip can be certainly inhibited, the operation is carried out favorably to improve working efficiency, and at the same time the life of the wheels is lengthened.
Further, a working vehicle may be a working vehicle having a modulating clutch which flexibly changes traveling power transmitted from an engine to a torque converter, and a controller which controls a degree of engagement of the modulating clutch so that vehicle speed becomes a predetermined value during operation, and it includes,
rotational frequency detectors which detect the rotational frequencies of right and left driving wheels of the vehicle, respectively, and
the controller controlling the degree of engagement of the modulating clutch by detecting a sign of a wheel slip based on a difference in the rotational frequency between the right and left driving wheels detected by the rotational frequency detectors, to prevent a slip.
According to the aforesaid structure, the control which makes vehicle speed to be a predetermined value is carried out and a sign of a wheel slip is detected based on the difference in the rotational frequency between the right and left driving wheels, thereby the degree of engagement of the modulating clutch being controlled to inhibit a slip. As a result, since the vehicle speed becomes a predetermined value, the working vehicle does not tend to travel too far during an operation such as excavation, and it is possible to carry out the operation efficiently. Additionally, even if a slip begins to occur, it can be certainly inhibited since the controller detects a sign of the slip and automatically controls the degree of engagement of the modulating clutch. Therefore, operation is carried out favorably to improve working efficiency, and at the same time the life of the wheels is lengthened.
Furthermore, a working vehicle may be a working vehicle having a modulating clutch which flexibly changes traveling power transmitted from an engine to a torque converter, and a controller which controls a degree of engagement of the modulating clutch, and it includes,
a rotational frequency detector which detects the rotational frequency of either right or left driving wheel of the vehicle, and
a shaft rotational frequency detector which detects the rotational frequency of any one of rotating shafts from an output shaft of the torque converter to an input shaft of a differential, and
the controller converting the rotational frequency of a rotating shaft detected by the shaft rotational frequency detector to the rotational frequency when transmitted to the right and left driving wheels, and controlling the degree of engagement of the modulating clutch by detecting a sign of a wheel slip based on a difference between the converted rotational frequency and the rotational frequency detected by the rotational frequency detector, to prevent a slip.
According to the above structure, more accurate slip detection is made possible, compared to when detecting a sign of a slip based on the difference in the rotational frequency between the right and left driving wheels. Therefore, a slip can be prevented more certainly.